1. Field of the Invention
The invention relates generally to a material handling system, particularly for handling pocketed coil strings.
2. Brief Description of the Prior Art
Pocketed coil strings have been used for many years in the manufacture of upholstered furniture and mattresses. A pocketed coil machine is used to make pocketed coil strings by inserting springs into pockets as shown in U.S. Pat. No. 5,749,133 and U.S. Pat. Nos. 5,613,287, 5,186,435, 4,565,046, and 4,439,977, assigned to the applicant of the current application. After the pockets are sealed, the springs are expanded within the pockets. Multiple pockets make up a string of pocketed coils.
These pocketed coil strings are typically stored and transported in large bins. The pocketed coil strings are loosely piled into the bin until the bin is full. U.S. Pat. No. 4,406,391 discloses an accumulator bin for handling strips of pocketed coil springs. The bins have casters mounted on the underside to facilitate movement. These bins are then moved around the manufacturing facility by hand. The bins filled with pocketed coil strings are manually transported to other areas of the facility for further use during the mattress or upholstered furniture manufacturing process.
In connection with the mattress manufacturing process, the strings are cut into smaller sections by another machine and attached together via gluing or some other manner known in the art to form an intermediate product known as a construction. These constructions are then used to manufacture a final product such as a mattress.
Alternatively, constructions could be shipped as subassemblies for final assembly into mattresses and furniture. For shipment, the constructions typically are compressed and strapped. Employee safety, however, is a concern when the straps on the compressed constructions are cut during the unwrapping process, and all of the springs in the constructions expand simultaneously.
Furthermore, logistical problems exist because a wide variety of constructions have to be shipped to mattress manufacturing facilities. Mattresses constructions are typically made in the following sizes: California King, King, Olympic Queen, Queen, Full XL, Full, Twin XL, and Twin. Each mattress size requires a different length of pocketed coil string. The various constructions are also available with different coils and different wire gauges. Thus, a mattress manufacturing facility must maintain a large and varied inventory of constructions for use in the final assembly of mattresses.
It is therefore an objective of this invention to provide an improved method of transporting and storing pocketed coil strings. This method would allow safe storage and transportation of pocketed coil strings while also being economical.
It is a further objective of this invention to provide an apparatus and system to facilitate this improved method of transporting and storing pocketed coil strings.
These and other objectives of the invention are accomplished by a system and method of storing and transporting pocketed coil strings in which the pocketed coil string is wound onto a spool with the springs in a compressed state. Instead of causing the expansion of the springs in the pockets of the pocketed coil strings after they are manufactured by a pocketed coil machine, the inventive method leaves the springs compressed within the fabric pockets of the pocketed coil string. With the springs compressed within the fabric pockets, a string spooling apparatus is then used to wrap the pocketed coil strings with compressed springs around a spool. The spool may be arranged to wrap the pocketed coil strings about either a vertical or a horizontal axis.
The wound packages of pocketed coil strings with compressed springs are then transported to another manufacturing facility, preferably with the axis of the spools oriented in the vertical direction so the wound packages do not roll around during transport. In order to utilize the pocketed coil strings, the pocketed coil strings are unwound from the spools. During the unwinding process, the compressed springs are allowed to expand in the pocketed coil string, one at a time, as the pocketed coil string is unwound. The pocketed coil string with expanded springs is then cut to the desired length for manufacturing the desired construction.
By wrapping the pocketed coil strings with compressed springs around a spool, substantially less space is used than by storing pocketed coil strings with expanded springs in bins. Furthermore, the present invention allows for greater flexibility in manufacturing because the constructions do not have to be made before shipping to a remote facility for final assembly. This reduces the need to manufacture a large variety of constructions for different end uses.
Moreover, transporting and handling of the wound package of pocketed coil strings is safer than transporting wrapped and banded constructions. When the ties on a wrapped and banded constructions are cut, the compressed springs in the constructions expand rapidly and simultaneously thereby causing a dangerous situation for employees. By contrast, when the wound package of the pocketed coil string is unwound, the spring tension within the pocketed coil string is relieved essentially one spring at a time as the pocketed coil string is unwrapped from the spool. Therefore, the danger of rapid expansion of a number of springs simultaneously is eliminated.